1. Field of the Invention
The invention relates to electronic parts mounted on printed circuit boards, and specifically to the technology of mounting electronic parts on printed circuit boards.
2. Description of Related Art
Conventional soldering apparatuses solder electronic parts on printed circuit boards all at once, as is the case with mass production. However, soldering is performed differently in the case of soldering pins which are adjacent to each other and separated by an extremely small space. The soldering pins are provided on adjacent electrode units which are likewise separated by an extremely small space corresponding to the separation of the pins on the printed circuit board. Machines which use this setup include a thermal head of a facsimile machine and a printer. In such a case, soldering is performed manually for each pin in order to prevent the formation of a soldering bridge.
For example, FIG. 1 shows a conventional manufacturing process for a printed circuit board. First, copper 2 is provided (step 1) on the board 1 as a conductive member. The board 1 is formed of phenol resin or a similar material.
Ink 3 is then coated (step 2) by printing on a section of the copper 2 on which a pattern is formed. The pattern is formed according to a pre-designed pattern arrangement. A portion of the copper 2 outside of the section on which the ink 3 is printed is removed by etching (step 3). Then, the pattern 4 is formed on the board 1 by removing the ink 3 which remained defining the pattern (step 4).
Next, in order to prevent short circuits between patterns 4 during soldering, a covering member 6 is provided on the pattern 4 and the board 1 by printing using a printing sheet having a printing pattern. The printing sheet has a transferring pattern except for the positions corresponding to the electrode units 5 in the patterns 4 and the covering member 6 is coated by insulated material through the transferring pattern (step 5). As a result, the board 1 and the patterns 4 are insulated except for the electrode units 5, and short circuits between the patterns 4 is prevented during soldering and similar operations. Subsequently, characters 7 and the like are provided on the covering member 6 by silk sheet printing to provide information regarding the process (step 6).
However, the pitch of pins in such machines is often only about 1 mm. Thus, numerous soldering bridges can still be formed even when soldering is performed manually.
Such soldering bridges are discovered only when the power source of the machine is turned on after manufacturing is completed. Discovering soldering bridges at this time lowers production efficiency.
This problem can be solved by widening the space between electrode units in the pattern. However, widening the space between electrode units makes the circuit board too large.